Crayfish are crustaceans that are also known as crawdads, crawfish, and freshwater lobsters; they are closely related to lobsters, crabs, and shrimp. There are about 150 crayfish species in North America, and over 540 species worldwide.

Crayfish live in streams, rivers, swamps, ponds, and other freshwater habitats. Most crayfish are strictly aquatic but some live in semi-aquatic environments. The semi-aquatic crayfish burrow into the soil to get to water (so that they can breathe).

Anatomy: This crustacean has a hard exoskeleton that protects and supports the body. The crayfish has 8 jointed walking legs, a segmented body, 2 pairs of sensory antennae, and compound eyes. It has 2 large pincers or claws called chelipeds. If a crayfish loses a leg, the leg will regenerate (regrow). The head and thorax are fused, forming the cephalothorax. Using gills, a crayfish breathes oxygen that is dissolved in water. Juvenile crawfish are light tan, but adults are deep red. Their color also depends on diet. As a crayfish grows, it often molts (loses its old shell and grows a new one). It eats the old shell. Crawfish in North America range from 2 to 6 inches (5-15 cm) long; Australian crawfish are larger.

Diet: Crayfish are omnivores; they eat plants, animals, and decaying organisms. They are nocturnal (most active at night) and eat fish, shrimp, water plants, worms, insects, snails, and plankton. Larval crayfish are very tiny; they eat plankton.